Phosphor Screen for MEMS Image Intensifiers

ABSTRACT

A phosphor screen for a Micro-Electro-Mechanical-Systems (MEMS) image intensifier includes a wafer structure, a lattice of interior walls, a thin film phosphor layer, and a reflective metal layer. The wafer structure has a naturally opaque top layer and an active area defined within the naturally opaque top layer. The lattice of interior walls is formed, within the active area, from the naturally opaque top layer. The thin film phosphor layer is disposed in the active area, between the lattice of interior walls. The reflective metal layer that is disposed atop the thin film phosphor layer. In at least some instances, the thin film phosphor layer is a non-particle phosphor layer.

BACKGROUND

Often, image intensifiers utilize phosphor screens in their design.These phosphor screens are typically created with particle phosphor;however, the processes for creating a phosphor screen with particlephosphor is quite burdensome and often yields a phosphor screen withundesirable characteristics. For example, at a high level, particlephosphor screens are often created by adhering (i.e., gluing) phosphorparticles to a fiber optics faceplate. One or more applications ofadhering materials and temperature bakes may be used in this process.Then, the phosphor particles are coated with aluminum (or another suchmetal), which often requires multiple steps in and of itself to minimizethe number of pinholes included in the aluminum layer.

For example, in order to create a uniform aluminum layer over thephosphor particles sacrificial planarizing materials may be used priorto the Aluminum deposition (and subsequently removed). Unfortunately,during this process, gas and water ends up trapped under the aluminumlayer, which creates “virtual leaks” in the phosphor screen that outgasduring device operation reducing the performance of the device. This isdetrimental to the reliability of the image intensifier.

Due, at least in part, to the difficulties associated with depositingparticle phosphor, many particle phosphor screens include substantiallyflat wafer structures (i.e., the aluminum or metal layer is a continuouslayer that extends substantially within a flat plane that is parallel toa top surface of the fiber optics faceplate). This continuous, flatshape allows light to transfer laterally away from an initial point ofcontact with the phosphor screen (i.e., allows phosphor scatter) andalso fails to prevent backscattered electrons from creating light awayfrom the initial point of contact (which creates a halo effect when theelectron re-enters at a different location).

Moreover, phosphor screens with particle phosphor are undesirable, ifnot incompatible, with Micro-Electro-Mechanical-Systems (MEMS) imageintensifiers, at least because particle phosphor typically has aparticle size (i.e., 2 microns in diameter) that is too large for highvolume wafer scale processing. For example, vacuum seals for a MEMSimage intensifier may be performed using a direct bond or bond materialsthat are less than 10 microns thick and linewidths that are between tensto hundreds of microns wide. Consequently, a phosphor particle with a 2micron diameter may break a wafer on which the image intensifier isformed or prevent a vacuum seal from being formed thereon.

In view of the aforementioned issues, a phosphor screen for MEMS imageintensifiers that does not include particle phosphor (and, thus, iscompatible with wafer scale processing) is desired. Such a phosphorscreen may be especially desirable if the phosphor screen can reducebackscattered electrons, minimize photon scatter, and/or reduce theamount of unintended virtual leaks (i.e., unintended gasses in thevacuum space) included in the phosphor screen (i.e., as compared tophosphor screens formed with phosphor particles).

SUMMARY

According to one embodiment, a phosphor screen for aMicro-Electro-Mechanical-Systems (MEMS) image intensifier includes awafer structure, a lattice of interior walls, a thin film phosphorlayer, and a reflective metal layer. The wafer structure has a naturallyopaque top layer and an active area defined within the naturally opaquetop layer. The lattice of interior walls is formed, within the activearea, from the naturally opaque top layer. The thin film phosphor layeris disposed in the active area, between the lattice of interior walls.The reflective metal layer that is disposed atop the thin film phosphorlayer. In at least some instances, the thin film phosphor layer is anon-particle phosphor layer.

According to another embodiment, a phosphor screen for a MEMS imageintensifier includes a wafer structure, a lattice of depressions, anon-particle phosphor layer, and a reflective metal layer. The waferstructure has an active area and the lattice of depressions is formedwithin the active area. The non-particle phosphor layer is disposed inthe depressions and the reflective metal layer is disposed atop thephosphor layer.

According to yet another embodiment, a method of forming a phosphorscreen for a microelectromechanical image intensifier includes creatinga pattern of pixels in an active area of a naturally opaque top layer ofa wafer. A phosphor layer is grown across the pattern of pixels and thephosphor layer is annealed. A reflective metal is deposited over thephosphor layer.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a perspective view of a die including a phosphorscreen for a Micro-Electro-Mechanical-Systems (MEMS) image intensifier,according to an example embodiment of the present invention.

FIG. 2 illustrates a cross-sectional view of the die of FIG. 1 takenalong line A-A from FIG. 1.

FIG. 3 illustrates a close-up view of inset B from FIG. 2.

FIG. 4 illustrates a high-level flow chart of a method for forming aphosphor screen for a MEMS image intensifier, according to an exampleembodiment of the present invention.

Like reference numerals have been used to identify like elementsthroughout this disclosure.

DETAILED DESCRIPTION

A phosphor screen for a Micro-Electro-Mechanical-Systems (MEMS) imageintensifiers is presented herein. The phosphor screen includes a thinfilm of phosphor that is formed (i.e., deposited) on a wafer structurewith a lattice of interior walls that form a plurality of cells orpixels. Notably, the phosphor screen does not include phosphor particlesand, instead, includes a thin film phosphor layer. Consequently, thephosphor screen is compatible with wafer scale processing. Thecells/pixels include or define open-top depressions or cavities and thephosphor layer is deposited on at least a bottom surface of eachdepression or cavity.

Advantageously, the lattice of interior walls contains or capturesbackscattered electrons. Moreover, since the phosphor layer is anon-particle layer (that is, since the phosphor layer does not includeany phosphor particles), the phosphor screen is substantially thinnerthan typical phosphor layers. For example, the phosphor layer of thephosphor screen presented herein may be a thin phosphor film with athickness of 200 nanometers (nm). By comparison, phosphor particlestypically have a diameter of 2 microns (i.e., 2,000 nm), which isapproximately 10 times larger than the thickness of the thin phosphorfilm included in the phosphor screen presented herein. Consequently, thephosphor screen presented herein may reduce photon scatter as comparedto phosphor screens with phosphor particles. Moreover, the non-particlephosphor layer defines a substantially flat or planar top surface and,thus, a reflective metal layer can be deposited directly onto thephosphor layer without any evaporation operations (i.e., lacquer neednot be applied and removed during formation of the phosphor screen).This minimizes the amount of unintended “virtual leaks” (i.e.,unintended vacuum space) included in the phosphor screen, especially ascompared to phosphor screens that include an irregular phosphor layer,such as those utilizing particle phosphor.

As mentioned, the phosphor screen presented herein is suitable for MEMSimage intensifiers. As a brief example, the phosphor screen presentedherein may be formed on 70-100 dies of a wafer for an image intensifierof night vision goggles. This phosphor screen may provide performanceadvantages that allow a system including the phosphor screen to besubstantially smaller and lighter than systems including particle-basedphosphor screens and, thus, may allow an image intensifier and/or a pairof night vision googles to be substantially smaller, in size and weight,than those incorporating particle-based phosphor screens. Moreover, thethin film phosphor layer may be approximately one-tenth the size ofphosphor layers formed from phosphor particles. When the phosphor screenpresented herein is included in night vision goggles, the phosphorscreen may convert amplified electrons back into visible light (afterother components of the goggles/image intensifier convert photonsreceived from ambient light to electrons and amplify the electrons). Theefficiency of the phosphor screen presented allows the phosphor screento output visible light that can be viewed in a direct view system(i.e., a system where a user looks directly at the phosphor for animage) or a digital system (i.e., a system where a user views a digitaloutput from a camera focused on the phosphor screen).

Now turning to FIG. 1, this figure illustrates a perspective view of adie 10 including an example embodiment of a phosphor screen 100 for aMEMS image intensifier. The phosphor screen 100 is included in activearea 12 (also referred to as an imagining area 12) of the die 10, whichin the perspective embodiment is a square with a height and width ofdimension D1. More specifically, in the depicted example, the activearea 12 is a square area that is approximately 14 millimeters (mm) by 14mm (i.e., D1 is 14 mm). However, in other embodiments, the active area12 may be any shape and size.

Regardless of the shape and size of the active area 12, the active area12 is bounded by an external band 16 that allows the die to be securedand sealed to additional components (i.e., to additional wafers with avacuum seal). In the depicted embodiment, the external band 16 is formedfrom a silicon layer 120. In fact, in the depicted embodiment, the die10 is a portion of a wafer 110, such as a glass wafer, with a siliconlayer 120 formed atop the wafer 110. The silicon layer 120 may be formedatop the wafer 110 with any techniques now known or developed hereafter,such as etchback bonding, thinning, and/or deposition. Moreover, thesilicon layer 120 may be bonded to the wafer 110 with any bond (e.g., ananodic bond, a crypt bond, etc.). Collectively, the wafer 110 and thesilicon layer 120 may be referred to as the wafer structure, with thesilicon layer 120 forming a top layer of the wafer structure.

Notably, the wafer structure includes a lattice of interior walls 130.The lattice of interior walls 130 is formed from the silicon 120 (in theactive area) and can be by selectively adding or removing materials tothe active area 12. In particular, the lattice of interior walls 130 isformed in the active area 12 by adding silicon 120 to the wafer 110 in aspecific pattern and/or by bonding silicon 120 to the wafer 110 andselectively removing silicon 120 from the wafer 110. For example, insome embodiments, the silicon layer 120 is deposited into the activearea 12 and patterned with lithography techniques, such as by patterninga silicon on insulator (SOI) wafer (which includes a thin layer ofsilicon separated from a handle wafer by an oxide), bonding the siliconof the SOI wafer to the wafer 110, and etching off the handle wafer toexpose the lattice of interior walls 130. By comparison, in otherembodiments, a uniform layer of silicon 120 is formed atop of the glasswafer 100 and then the silicon 120 is selectively removed in order toform the lattice of interior walls 130. Put generally, the waferstructure can be formed in any manner that defines a lattice of interiorwalls 130 in the active area 12.

Moreover, regardless of how the lattice of interior walls 130 is formed,the lattice of interior walls 130 will be naturally opaque becausesilicon is naturally opaque. Consequently, the walls 130 do not need tobe coated (or overcoated) with reflective and/or absorptive material.That is, due to their natural opacity, the lattice of interior walls 130(which is formed from the silicon 120) will absorb and/or reflect lightand prevent, or at least minimize, the deleterious effects ofbackscattered electrons. Put still another way, the naturally opaquelattice of interior walls 130 do not require any modifications, such asa treatment to create a reflective layer, to prevent light fromtraveling through the walls 130, between cells or pixels 135 defined bythe lattice of interior walls 130.

FIGS. 1-3 are now referred to for a description of the pixels 135.Generally, the lattice of interior walls 130 defines a pattern of pixelsor cells 135 within the silicon layer 120. However, the pixels 135 donot actually include any silicon therein; the bottom of the pixel isinitially formed from the wafer 110 and eventually covered with the thinphosphor film 140 and the reflective metal layer 150. Put another way,the silicon 120 is removed from a bottom 136 of each pixel 135. Thus,when the pixels 135 are described as being formed in the silicon 120,this is intended to mean that the pixels 135 are formed between walls130 that are formed from the silicon 120 and are simply disposed, inlarge part, in alignment with the silicon layer 120.

In the depicted embodiment, the pixels 135 are uniform pixels. That is,the pixels 135 are patterned in a regular, repeating pattern, insofar asthe pixels 135 each have the same dimensions and are separated by thesame distance. For example, each pixel 135 may have a square bottomsurface 136 with a length and width (depicted as W1 in FIG. 3) in therange of approximately 4 microns to approximately 6 microns. Meanwhile,each pixel 135 may have a height (depicted as H in FIG. 3) in the rangeof approximately 4 microns to approximately 10 microns and each wall 130may have a thickness of approximately 0.3 microns so that adjacentpixels 135 are separated by a distance of approximately 0.3 microns(depicted as W2 in FIG. 3). Notably, the height (i.e., H from FIG. 3) ofthe pixels may be substantially shorter than similar structures usedwith particle phosphor, at least because the film phosphor layer 140 issubstantially thinner (i.e., has a shorter height) than a particle-basedphosphor layer, as is discussed in further detail below.

When the phosphor screen 100 is formed with the aforementioneddimensions, the phosphor screen 100 may have an open area ratio ofapproximately 88%. That is, the pixels 135 may cover approximately 88%of the phosphor screen's normal surface area (the surface area seen froma normal position relative to the phosphor screen 100 (the top of thepage in the Figures when viewed in landscape)). However, in otherembodiments, the open area ratio may be in the range of approximately80% to 95%. Higher open area ratios may serve to more effectively reducebackscattered electrons (since higher open area ratios reduce the chanceof an electron impacting a top surface 132 (see FIG. 3) of a wall 130),but the open area ratio must also be balanced against the structuralintegrity of the lattice of interior walls 130 and the size of thepixels 135. Notably, wall thickness and pixel size may control the openarea ratio, but thinner walls may be more unstable and larger pixels 135may be less effective in preventing backscattered electrons fromre-impacting a phosphor layer 140 included at a bottom 136 (see FIG. 3)of the pixel 135.

Now referring to FIGS. 2 and 3, these figures illustrate a crosssectional view of the die 10 taken along line A-A from FIG. 1 and aclose-up view of a portion B from FIG. 2, respectively. These figuresdepict the thin film of phosphor 140, which is disposed across thepattern of pixels 135 defined by the lattice of interior walls 130,insofar as the term “across” signifies that that the phosphor layer 140is disposed at least between any and all interior walls of the latticeof interior walls 130. That is, the phosphor layer 140 is disposed on atleast the bottom surface 136 of each of the cells/pixels 135 that aredefined by the lattice of interior walls 130, so that the phosphor film140 covers at least a portion of the active area 12 equivalent to theopen area ratio (i.e., 80-95%) when the phosphor screen is viewed from adirection normal to the major dimension of the phosphor screen 100(i.e., from a top of the page in the Figures when viewed in landscape).

That being said, often deposition techniques cannot distinguish betweenthe walls 130 and the pixels 135 and, thus, the layer of phosphor 140may be disposed between the lattice of walls 130 and atop the lattice ofwalls 130. That is, the phosphor film 140 may be deposited on a bottomsurface 136 of each pixel 135 and a top surface 132 of each wall 130, asis clearly shown in FIG. 3, so that the phosphor film 140 covers 100% ofthe active area, when the phosphor screen is viewed from a directionnormal to the major dimension of the phosphor screen 100 (i.e., from atop of the page in the Figures when viewed in landscape).

Still further, in some embodiments, the phosphor layer 140 may also coatthe sidewalls 134 of any walls 130, thereby completing coating anysurfaces defining a pixel 135. For example, if the phosphor layer 140 isformed via atomic layer deposition, the phosphor layer 140 may coat thebottom 136 and all four sidewalls 134 surrounding the bottom 136. Forclarity, side walls 134 that are normal to the sectional view (i.e.,walls of pixel 135 that would be considered back walls from theperspective of the sectional view) are omitted from FIGS. 2 and 3;however, it is to be understood that the sidewalls 134 may substantiallysurround or bound the bottom 136 of each pixel 135, as is shown inFIG. 1. Moreover, the sidewalls 134 may extends substantiallyperpendicular to the bottom 136 (i.e., the sidewalls 134 may besubstantially vertical sidewalls 134) so that each pixel 135 isessentially an open-top cavity or depression. Additionally oralternatively, the shape of each pixel 135 may be described as a pit ortrench.

Despite the mention of atomic layer deposition above, the non-particlephosphor layer 140 may be formed across the lattice of interior walls130 with any number of deposition techniques suitable for depositing anon-particle phosphor film with a suitable height that ensures electronenergy is deposited into the non-particle phosphor layer. A suitableheight may be any height greater than a penetration range of incomingelectrons. The penetration range may depend upon the energy of anincoming electron and a density of the phosphor, with the relationshipbeing defined by the equation

${R_{P} = {\frac{0.1V_{landing}^{1.5}\left\{ {kV} \right\}}{\rho \left\{ {g\text{/}{cm}^{3}} \right\}}\left\{ {\mu m} \right\}}},$

with ρ representing phosphor density, V representing energy of theincoming electron and R_(p) representing the penetration range. Thatbeing said, the thickness of the phosphor should also be minimized inview of the penetration range to minimize deleterious effects on screenresolution (R_(L)), which is defined by the equation

$R_{L} = {\frac{500}{{Thickness}\mspace{14mu} \left\{ {\mu m} \right\}}{\left\{ {{lp}\text{/}{mm}} \right\}.}}$

As a more concrete example, when electron energy is absorbed overapproximately 200 nm (i.e., penetration range is 200 nm, which may bemost common), the height of the non-particle phosphor film 140 is in therange of approximately 200 nm to 300 nm. Consequently, the thin film 140is sufficient to absorb electron energy and convert the energy tovisible light. Moreover, this height (i.e., thickness of the film) maybe approximately one-tenth the size of phosphor layers formed fromphosphor particles and the reduced height of the phosphor layer 140,which, to reiterate, is anon-particle phosphor film, may serve to reducephoton scatter within the phosphor layer (i.e., as compared to aparticle-based phosphor layer).

Still referring to FIGS. 2 and 3, a layer of reflective metal 150 isdisposed atop the layer of phosphor 140. That is, the layer of phosphor140 is coated with a reflective metal layer 150. The reflective metallayer 150 may be a layer of aluminum, magnesium, beryllium, and/or anyother conductive and reflective metals (i.e., metals with low atomicnumbers) and can be formed directly atop of the phosphor layer 140,without any evaporation techniques. That is, the reflective metal layer150 can be deposited directly onto a top surface of the phosphor layer140 without applying a lacquer in between the two depositions (andwithout subsequently attempting to remove the lacquer via heating). Thereflective layer 150 can be formed directly atop of the phosphor layer140 because the phosphor layer 140 forms a substantially planar topsurface (i.e., a substantially flat top surface), albeit a discontinuousplanar top surface (i.e., the top surface is actually a plurality ofplanar top surface segments, separated by the lattice of walls 130).Forming the reflective layer 150 directly atop of the phosphor layer 140creates substantially fewer pinholes, virtual leaks, and trapped gas, ascompared to techniques that apply and subsequently remove (i.e., burnout) a lacquer or other such substance.

Now referring to FIG. 3, the overall structure of the lattice ofinterior walls 130 (and the pixels 135 formed by the interior walls)substantially reduces electron scatter. When electrons are bombardedagainst any phosphor screen, at least some of the electrons will bounceaway from the phosphor screen (i.e., backscatter), but the phosphorscreen presented herein reduces or eliminates the negative impact ofthis backscattering (i.e., the phosphor screen presented herein reducesor eliminates the “halo effect”). The phosphor screen 100 prevents thenegative impact because the lattice of interior walls 130 prevents theelectrons from traveling laterally into another pixel 135. Instead, andas is shown in FIG. 3, a backscattered electron will be absorbed intoone of the sidewalls 134 or reflect off of one of the sidewalls 134(which directs a backscattered electron away from the phosphor layer140).

FIG. 4 illustrates a high-level flow chart of a method for forming aphosphor screen for a MEMS image intensifier, according to an exampleembodiment of the present invention. Initially, at step 410, a patternof pixels is created in an active or imaging area of a die of a wafer.As is shown at 412 and 414 (and as is described above), in someembodiments, forming the pixels involves providing a wafer with a toplayer of silicon and creating a lattice of walls in the silicon todefine a pattern of pixels. As is described above, in variousembodiments, a silicon layer may be deposited on and/or bonded to (i.e.,anodically bonded) a wafer, such as a glass wafer, and the lattice ofinterior walls may be formed with various lithography and/or depositiontechniques.

At 420, a layer of phosphor is grown or formed across the lattice ofpixels. As is described above, the layer of phosphor is a non-particlephosphor and is applied with any deposition techniques now known ordeveloped hereafter. Consequently, in growing the layer of phosphoracross the lattice of pixels, the layer of phosphor may be deposited atthe bottom of each pixel and may also be deposited atop of each wall inthe lattice of walls. In fact, in some embodiments (i.e., thoseembodiments in which the phosphor layer is deposited with atomic layerdeposition), the phosphor layer may also be deposited on the side wallsof each wall in the lattice of walls.

At 430, the phosphor layer is annealed. The annealing crystallizes thephosphor layer and ensures that the phosphor layer has a good phosphorefficiency (so that the phosphor layer converts as much energy from anelectron thereon into light). The annealing may require the phosphorlayer to be heated to a temperature in the range of 600-900° C. Notably,since the lattice of interior walls (absorbers/reflectors) is formedwith Silicon rather than glass overcoated with aluminum, the interiorwalls may allow for a higher anneal point, at least in comparison toglass overcoated with aluminum. This higher anneal point may improvephosphor efficiency (which, in turn, creates visible light suitable fordirect viewing or digital applications). By comparison, if glassovercoated with aluminum is annealed at temperatures in the range of600-900° C., the aluminum may melt and/or diffuse into the glass (sincealuminum melts at 660° C.). Consequently, glass overcoated with aluminumis annealed at lower temperatures that produce a lower phosphorefficiency.

At 440, a reflective metal layer is deposited over the annealed phosphorlayer. As mentioned above, the reflective metal layer may be a layer ofaluminum, magnesium, beryllium, and/or any other conductive andreflective metals (i.e., metals with low atomic numbers) and may coverany phosphor layer deposited into the pixels or onto the lattice ofinterior walls. For example, if the phosphor layer is deposited withatomic layer deposition techniques, the reflective metal layer may bedeposited over the phosphor film disposed at the bottom of a pixel(i.e., item 136 of FIG. 3), the side walls defining the pixel (i.e.,items 134 of FIG. 3), and the top of the interior walls forming thepixel (i.e., item 132 of FIG. 3). When the reflective metal layer isdeposited onto all of these surfaces, the reflective metal layer may beconnected electrically across the active area; however, in embodimentswhere the phosphor layer (and, thus, the reflective metal layer) is onlydisposed at the bottom of the pixels and/or the tops of the interiorwalls, the portions of reflective metal layer may each be electricallyinsulated.

To summarize, in one form, a phosphor screen for amicroelectromechanical image intensifier is provided, comprising: awafer structure with a naturally opaque top layer and an active areadefined within the naturally opaque top layer; a lattice of interiorwalls is formed from the naturally opaque top layer within the activearea; a thin film phosphor layer that is disposed in the active areabetween the lattice of interior walls; and a reflective metal layer thatis disposed atop the thin film phosphor layer.

In another form, a method of forming a phosphor screen for amicroelectromechanical image intensifier is provided, comprising:creating a pattern of pixels in an active area of a naturally opaque toplayer of a wafer; growing a phosphor layer across the pattern of pixels;annealing the phosphor layer; and depositing a reflective metal over thephosphor layer.

In yet another form, a phosphor screen for a microelectromechanicalimage intensifier is provided, comprising: a wafer structure with anactive area; a lattice of depressions formed within the active area; anon-particle phosphor layer that is disposed in the depressions; and areflective metal layer that is disposed atop the phosphor layer.

The phosphor screen presented herein provides a number of advantages.For example, as is discussed above, the wafer structure (i.e., thestructure of the glass wafer and silicon that forms the lattice ofinterior walls and pattern of pixels) captures backscattered electrons,which improves the image fidelity (i.e., as measured via the modulationtransfer function) of the phosphor screen. The wafer structure may alsobe conductive to draining charge away from the phosphor screen andimprove phosphor efficiency (i.e., by allowing for a higher annealpoint).

As another example, due, at least in part, to the thin film phosphorlayer, the phosphor screen presented herein may reduce photon scatter(at least as compared to particle-based phosphor screens) and, thus, mayimprove image fidelity (i.e., as measured via the modulation transferfunction) by eliminating phosphor cross talk between pixels. Stillfurther, the phosphor screen presented herein may reduce or eliminatevirtual leaks because there is no evaporation processing necessary toform a reflective metal layer atop of phosphor particles (which definean irregular top surface). Instead, reflective metal can be applied(i.e., deposited) directly to a flat top surface of the thin filmphosphor layer. That being said, prior to forming the phosphor layer,reflective metal need not be applied to the wafer structure at leastbecause the silicon interior walls are naturally opaque.

As a final example, since the phosphor screen presented herein does notinclude phosphor particles, the phosphor screen is compatible with waferscale processing and hermetic sealing. Consequently, the phosphor screencan be rapidly produced at scale and quickly and efficientlyincorporated into various imaging products, such as night vision gogglesor scopes. In fact, the phosphor screens presented herein may improvethese imaging products by providing a size and weight reduction ascompared to particle-based phosphor screens. The phosphor screen mayalso provide a performance improvement for both digital and analogsolutions by improving the image fidelity of the image produced by thephosphor screen.

It is to be understood that terms such as “left,” “right,” “top,”“bottom,” “front,” “rear,” “side,” “height,” “length,” “width,” “upper,”“lower,” “interior,” “exterior,” “inner,” “outer” and the like as may beused herein, merely describe points or portions of reference and do notlimit the present invention to any particular orientation orconfiguration. Further, the term “exemplary” is used herein to describean example or illustration. Any embodiment described herein as exemplaryis not to be construed as a preferred or advantageous embodiment, butrather as one example or illustration of a possible embodiment of theinvention.

Although the disclosed inventions are illustrated and described hereinas embodied in one or more specific examples, it is nevertheless notintended to be limited to the details shown, since various modificationsand structural changes may be made therein without departing from thescope of the inventions and within the scope and range of equivalents ofthe claims. For example, in some embodiments, the wafer described hereinmay be a fiber optic wafer that is masked and etched to form the latticeof interior walls. In these embodiments, the lattice of interior wallsmay then need to be coated in reflective and/or conductive material inorder to ensure that the interior walls are sufficiently opaque tocontain backscattered electrons. Then, a thin film phosphor andreflective material may be formed in pixels formed by the lattice ofwalls in the same manner as described above.

In addition, various features from one of the embodiments may beincorporated into another of the embodiments. Accordingly, it isappropriate that the appended claims be construed broadly and in amanner consistent with the scope of the disclosure as set forth in thefollowing claims.

1. A phosphor screen for a microelectromechanical image intensifier,comprising: a wafer structure with a naturally opaque top layer and anactive area defined within the naturally opaque top layer; a lattice ofinterior walls formed from the naturally opaque top layer to define aplurality of pixels within the active area; a thin film phosphor layerthat is disposed directly on a bottom of each pixel of the plurality ofpixels, between the lattice of interior walls; and a reflective metallayer that is disposed atop the thin film phosphor layer.
 2. Thephosphor screen of claim 1, wherein the thin film phosphor layer is anon-particle phosphor layer.
 3. The phosphor screen of claim 2, whereinthe thin film phosphor layer has a thickness in the range ofapproximately 200-300 nanometers.
 4. (canceled)
 5. The phosphor screenof claim 1, wherein the bottom of each pixel is a planar surface boundedby approximately vertical sidewalls.
 6. The phosphor screen of claim 1,wherein the wafer structure comprises: a glass wafer; and a siliconlayer bonded to a top surface of the glass wafer, the silicon layerforming the naturally opaque top layer.
 7. The phosphor screen of claim6, wherein the silicon layer is removed from a bottom of each pixel ofthe plurality of pixels.
 8. The phosphor screen of claim 7, wherein theplurality of pixels is provided in a regular, repeating pattern.
 9. Thephosphor screen of claim 1, wherein the lattice of interior creates anopen area ratio in the range of approximately 80-95%.
 10. The phosphorscreen of claim 1, wherein the thin film phosphor layer defines a planartop surface and the reflective metal layer is deposited directly ontothe planar top surface without an evaporation operation.
 11. A method offorming a phosphor screen for a microelectromechanical imageintensifier, comprising: creating a pattern of pixels in an active areaof a naturally opaque top layer of a wafer; growing a phosphor layerdirectly on a bottom of each pixel of the pattern of pixels; annealingthe phosphor layer; and depositing a reflective metal over the phosphorlayer.
 12. The method of claim 11, wherein the phosphor layer is anon-particle phosphor layer.
 13. The method of claim 11, wherein thenaturally opaque top layer is a silicon layer and creating the patternof pixels further comprises: creating a lattice of interior walls fromthe silicon layer that defines the pattern of pixels.
 14. The method ofclaim 13, wherein creating the lattice of interior walls furthercomprises: etching the silicon layer to remove material from the siliconlayer and define the lattice of interior walls.
 15. (canceled)
 16. Themethod of claim 11, further comprising: depositing the phosphor layeratop the lattice of interior walls.
 17. The method of claim 11, whereindepositing the reflective metal layer further comprises: depositing thereflective metal layer directly onto a planar top surface of thephosphor layer without an evaporation operation.
 18. A phosphor screenfor a microelectromechanical image intensifier, comprising: a waferstructure with an active area; a lattice of depressions formed in anaturally opaque top layer of the wafer within the active area so thatthe naturally opaque layer defines a plurality of pixels, wherein eachdepression in the lattice of depressions includes a bottom and aplurality of side walls; a non-particle phosphor layer that is disposeddirectly on the bottom of each of the depressions; and a reflectivemetal layer that is disposed atop the phosphor layer.
 19. (canceled) 20.The phosphor screen of claim 18, wherein the non-particle phosphor layeris deposited onto the plurality of side walls of each depression. 21.The phosphor screen of claim 1, wherein the interior walls are uncoatedinterior walls.
 22. The phosphor screen of claim 1, wherein the interiorwalls extend above the reflective metal layer so that the interior wallscan prevent electrons that backscatter in one of the plurality of pixelsfrom traveling laterally into another pixel of the plurality of pixels.23. The phosphor screen of claim 22, wherein the interior walls absorbor reflect the electrons that backscatter in the one of the plurality ofpixels.